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Water as a conductor?

Discussion in 'General Electronics Discussion' started by sid2286, Sep 2, 2016.

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  1. sid2286

    sid2286

    102
    1
    Aug 24, 2011
    I am trying to use water as a conductor, knowing water is a bad conductor.

    what i want to achieve is when two metal rod get in contact with water a relay must switch on.

    at this moment, when I short the two rods using copper wire the relay is triggered, however the same is not happening incase of water.

    is there anyway this can be achieved?
     
  2. duke37

    duke37

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    Jan 9, 2011
    Water is a very good insulator. It is used to cool radio valve anodes at several kV.
    Impure water with ionic salts will conduct, the resistance will depend on the water purity.
    To make your system more sensitive, then an amplifier will be needed. A single fet may be enough.
    Use a diode across the relay coil to reduce the voltage spike on switch off.
     
  3. shrtrnd

    shrtrnd

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    Jan 15, 2010
    When I was a kid I made a water detection alarm for my parent's basement out of a CD4011. The basement used
    to flood from sewer line back-up every few years.
    What I discovered is that clean water when I tested my circuit would not trigger it.
    Water is, as duke37 pointed-out, a pretty good insulator.
    The sewer water conducted for my water detection alarm without any problems.
    Water won't conduct very well with sensitive circuits, but contaminated water will. You would not be conducting
    through the water, you would be conducting through whatever 'contaminant' you add to the water.
    I don't know your application. If you are trying to trip your relay using a clean water source, I'd Google the project
    and see what other people have come up with using the new semiconductors available. If you can 'contaminate' the water source you want to trip your relay with, look for some type of (probably) mineral salts that won't hurt your metal
    detection rods, but will conduct.
    Out of curiosity, can't you use a float-level switch or some other method of activation?
    Is this a critical application when you can justify using an optical or capacitive detection circuit, or is this something
    you want to do on the cheap?
    All Electronics Van Nuys, CA is a surplus seller. They list a float switch with integrated thermistor (catalog #FLW-1) for $5 (U.S.) or cheaper in quantity as an example. There are a lot of float switches out there, probably also a lot of plans for water detection using electronic circuits on Google as well.
    Good luck
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Fortunately most water is impure and do contain conductive minerals. The FET circuit that Duke eluded to will look something like this. I included R2 as a safety in the case that Water Level Probe 1 should ever make contact with circuit GND. The value of R1 isn't critical but the higher it is the more sensitive this circuit will be.

    Chris
    upload_2016-9-2_11-46-5.png
     
    Tha fios agaibh and davenn like this.
  5. Alec_t

    Alec_t

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    Jul 7, 2015
    If you make R1 a variable resistor (say 500k) you could vary the sensitivity.
     
    CDRIVE likes this.
  6. cjdelphi

    cjdelphi

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    Oct 26, 2011
    A darlington combo with a 10k pull down on base should do the job...

    Grab a multimeter and test samples of conductivity (ohms)
     
  7. cjdelphi

    cjdelphi

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    Oct 26, 2011
    I'd not use salt to increase conductivity or you're going to corrode the rods far faster
     
  8. Anon_LG

    Anon_LG

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    Jun 24, 2014
    Use graphite or glassy carbon rods. Burn pencils to extract the graphite, HB's will do.
     
  9. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    If all you want to do is sense presence of water at some level, try this:

    [​IMG]
     
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  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Hop, that's just toooooooo cool! No electrolysis either! Will sedimentary deposits on the fiber optics affect it?

    Chris
     
  11. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    This is a specific implementation of a general optical concept called frustrated total internal reflection (FTIR). You can demonstrate the concept easily using an ordinary prism with a flat bottom and two sides that are at 45 degree angles to the bottom. Shine a laser pointer into the prism bottom and it bounces off the two sides and returns back to you, displaced some distance depending on how far the entrance beam is from the prism apex. Now submerge the apex of the prism in water (or some other transparent liquid) and observe the diminished return beam.

    I haven't done it yet, but I think this would be "easy" to fabricate from a solid Lexan plastic rod, say an inch or so in diameter. Just drill two shallow holes in one end to accept an LED and a photodetector. Then file and polish two flats on the other end with a 90 degree angle at the tip. The rod length is probably not important, but a shorter rod, say two or three inches long by one inch or less in diameter, might give better results. Of course you can also couple to an off-the-shelf prism with fiber optics, attaching the emitter and detector to separate fibers. Or just make it like the diagram shows from a single fiber.

    I have been fascinated with FTIR ever since, as a youngster, I observed the optical effects of staring into a fish aquarium from various points of view. Why, I asked myself, does one side appear to act like a mirror unless something is pressing against that side (as with a finger)? And what do the fish see? A mirror? Or a transparent wall? Turns out there is a lot of theory associated with evanescent waves used to explain the phenomenon. We barely touched on this in the electrical engineering field theory and optical physics classes I took during my college studies. Here is an excellent You Tube video that explains how evanescent waves get created. Ah luv thet suthen drawl the commentator has! Reminds me of the time of my youth when I lived in the South.
     
    Anon_LG likes this.
  12. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Hop, I'm sure you remember your posts where you pondered buying a live aboard boat. I know I told you that you should test the waters (so to speak) first. Never mind that... Buy the boat!

    PS: What southern drawl? Besides that,... absolutely everything reminds you of something! .... GET THE BOAT!! :D

    Chris
     
  13. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Hurricane Hermine this week convinced me that living on a boat is not a good idea. My step-daughter, who lives in a house on more or less dry land in Virginia Beach, VA, is getting pounded by the remnants of this now-tropical storm as I write this. And soon they will be pounded with snow as winter sets in.

    They really like their boats in the Norfolk area, with sizes ranging from little dinghies and daysailers up to and including houseboats and nuclear powered aircraft carriers, the latter being my idea of a decent and ideal "houseboat," except for the huge upkeep cost... they do make excellent ice cream on carriers, though, so if I could afford it that is what I would have as my houseboat.
     
    CDRIVE likes this.
  14. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    We'll set our sights a tad lower then. Go for getting in touch with things that you can see, feel, smell and touch. Like nature! ;)
    My favorite wildlife is the 'Double Breasted Bi-Pod Thong', found mostly along the shoreline. :)
    Chris
     
  15. hevans1944

    hevans1944 Hop - AC8NS

    4,581
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    Jun 21, 2012
    This is how I keep the brain cells from atrophying as I get older. Remembering things and solving puzzles (like why do I spend so much time here on EP) is supposed to aid in retaining higher brain functions, but maybe that isn't working for me. Ask Steven Hawking about that, although I hear from online adverts that his powers are chemically augmented with "all natural" dietary supplements. Free samples: just pay postage and handling and subscribe for a regular supply delivered right to your mailbox. What a wunnerful world we live in! Think I will look into male enhancement products next week. I've always wanted an Arnold Schwarzenegger physique without the bother of all that weight lifting.

    I love to hear the sound of surf breaking on the beach. And the sound of a mountain brook babbling down the rocks in the Spring when the snowmass is melting. One of my favorite childhood memories is Dad in his waders fly-fishing in a Colorado stream near Lyons, CO and catching a mess of rainbow trout for breakfast, prepared at our parachute-tent camp site beside the stream.

    US-36 gets you to Lyons from Denver, and from there over some mountains to Estes Park, CO. From there you can continue on US-36 up into the mountains. Haven't been there in many years, but even back then it was a well-paved, if narrow, two-lane road. I understand it is now a the conduit for well-maintained tourist traps.

    Colorado came in during the late 1950s and blasted some more mountain away, the granite boulders and silt ending up in Dad's fishing creek, effectively ruining it for fishing. It may or may not have recovered by now. My current wife has no interest in our re-visiting places I once cherished in the American West.

    My first wife didn't complain (much) when we did just that in 1978, driving two cars with two young children, a brand-new baby, and my mother to "celebrate" my upcoming graduation from college. I don't think she enjoyed the Grand Tour as much as I did when Dad performed it in 1954. He must have seen the "writing on the wall" because he took a month of paid leave to allow us to journey from Lake Charles, Louisiana, through Texas to visit Carlsbad Caverns in New Mexico, the mountains of Colorado (including our namesake, Mt. Evans), Yellowstone National Park, Wyoming, and Mount Rushmore before finally heading back with a side trip to Chicago to watch a Chicago White Sox vs Baltimore Orioles summer baseball game. This was the first year for the Orioles in MLB and IIRC they didn't do well that year and lost the game we attended.

    Back in the day, Estes Park was the last place you could gas up before heading further on up into the mountains. There was a single gas station with a hand-pump that allowed you to fill a glass reservoir with gasoline from an underground tank. You then emptied the reservoir by gravity into your vehicle tank through a hose and the usual hand-valve. Nice thing about this gas station was they also sold, in addition to the usual "Ethyl," "white" un-leaded gasoline for use in our Coleman stove and lanterns. It is my understanding that these "gas pumps" are quite the collector's item today. See image of one below, looking very much like the one I remember Dad using..

    [​IMG]

    I like to look closely at those too. I call them flowers. This because one day I was ogling some particular handsome specimens and my wife caught me staring. She asked, "WHAT ARE YOU DOING!" in that tone of voice that meant she didn't appreciate what I was doing. Thinking quickly, I noticed there were some flowers for sale outside the Sears Hardware store where the lovelies were walking by, that store being the reason we were there in the first place. So, I promptly replied, "Oh, nothing, just looking at those lovely flowers over there..." She didn't buy it of course, but I got some points for quick thinking. So from then on, I can point out a Double-Breasted Bi-Pod Thong and call it to her attention by shouting out, "Hey! Look, Hunny Bunny! FLOWERS!" Of course I am not allowed to actually pick any flowers and take them home.

    Hop
     
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